makecform() - Image Processing

C = makecform(type) creates
the color transformation structure C that defines
the color space conversion specified by type.
To perform the transformation, pass the color transformation structure
as an argument to the applycform function.The type argument specifies one of
the conversions listed in the following table. makecform supports
conversions between members of the family of device-independent color
spaces defined by the CIE, Commission Internationale de
l'Éclairage (International Commission on Illumination).
In addition, makecform also supports conversions
to and from the sRGB and CMYK color
spaces. For a list of the abbreviations used by the Image Processing Toolbox™ software
for each color space, see the Remarks section of this reference page.TypeDescription
'cmyk2srgb'Convert from the CMYK color space
to the sRGB color
space.
'lab2lch'Convert from the L*a*b* to
the L*ch color
space.
'lab2srgb'Use lab2rgb instead.
'lab2xyz'Use lab2xyz instead.
'lch2lab'Convert from the L*ch to
the L*a*b* color
space.
'srgb2cmyk'Convert from the sRGB to
the CMYK color space.
'srgb2lab'Use rgb2lab instead.
'srgb2xyz'Use rgb2xyz instead.
'upvpl2xyz'Convert from the u′v′L to
the XYZ color
space.
'uvl2xyz'Convert from the uvL to
the XYZ color
space.
'xyl2xyz'Convert from the xyY to
the XYZ color
space.
'xyz2lab'Use xyz2lab instead.
'xyz2srgb'Use xyz2rgb instead.
'xyz2upvpl'Convert from the XYZ to
the u′v′L color
space.
'xyz2uvl'Convert from the XYZ to
the uvL color
space.
'xyz2xyl'Convert from the XYZ to
the xyY color
space.
C = makecform(type, 'WhitePoint',
WP) specifies the value of the reference white point. type can
be either 'xyz2lab' or 'lab2xyz'. WP is
a 1-by-3 vector of XYZ values scaled so that Y =
1.  The default is whitepoint('ICC'). Use the whitepoint function
to create the WP vector.C = makecform(type, 'AdaptedWhitePoint',
WP) specifies the adapted white point. type can
be either 'srgb2lab', 'lab2srgb', 'srgb2xyz',
or 'xyz2srgb'. As above, WP is
a row vector of XYZ values scaled so that Y =
1. If not specified, the default adapted white point is whitepoint('ICC').
To get answers consistent with some published sRGB equations,
specify whitepoint('D65') for the adapted white
point.C = makecform('srgb2cmyk', 'RenderingIntent', intent) and C = makecform('cmyk2srgb', 'RenderingIntent', intent) specify
the rendering intent for transforms of type srgb2cmyk and cmyk2srgb.
These transforms convert data between sRGB IEC61966-2.1
and "Specifications for Web Offset Publications" (SWOP) CMYK. intent must
be one of these strings: 'AbsoluteColorimetric',
 'Perceptual', 'RelativeColorimetric',
 or 'Saturation'. For more information, see the
table Rendering Intent.C = makecform('adapt', 'WhiteStart', WPS, 'WhiteEnd',
WPE, 'AdaptModel', modelname) creates
a linear chromatic-adaptation transform. WPS and WPE are
row vectors of XYZ values, scaled so that Y =
1, specifying the starting and ending white points. modelname is
either 'vonKries' or 'Bradford' and
specifies the type of chromatic-adaptation model to be employed. If 'AdaptModel' is
not specified, it defaults to 'Bradford'.C = makecform('icc', src_profile, dest_profile) creates
a color transform based on two ICC profiles. src_profile and dest_profile are
ICC profile structures returned by iccread.C = makecform('icc', src_profile, dest_profile,
'SourceRenderingIntent', src_intent, 'DestRenderingIntent', dest_intent) creates
a color transform based on two ICC color profiles, src_profile and dest_profile,
specifying rendering intent arguments for the source, src_intent,
and the destination, dest_intent, profiles.Rendering intents specify the style of reproduction that should
be used when these profiles are combined. For most devices, the range
of reproducible colors is much smaller than the range of colors represented
by the PCS. Rendering intents define gamut mapping techniques. Possible
values for these rendering intents are listed below. Each rendering
intent has distinct aesthetic and color-accuracy trade-offs.Rendering IntentValueDescription
'AbsoluteColorimetric'Maps all out-of-gamut colors to the nearest gamut surface
while maintaining the relationship of all in-gamut colors. This absolute
rendering contains color data that is relative to a perfectly reflecting
diffuser.
'Perceptual' (default)Employs vendor-specific gamut mapping techniques for
optimizing the range of producible colors of a given device. The objective
is to provide the most aesthetically pleasing result even though the
relationship of the in-gamut colors might not be maintained. This
media-relative rendering contains color data that is relative to the
device's white point.
'RelativeColorimetric'Maps all out-of-gamut colors to the nearest gamut surface
while maintaining the relationship of all in-gamut colors. This media-relative
rendering contains color data that is relative to the device's white
point.
'Saturation'Employs vendor-specific gamut mapping techniques for
maximizing the saturation of device colors. This rendering is generally
used for simple business graphics such as bar graphs and pie charts.
This media-relative rendering contains color data that is relative
to the device's white point.
C = makecform('clut', profile, LUTtype) creates
the color transformation structure C based on a
color lookup table (CLUT) contained in an ICC color profile. profile is
an ICC profile structure returned by iccread. LUTtype specifies
which clut in the profile structure
is to be used. Each LUTtype listed in the
table below contains the components of an 8-bit or 16-bit LUTtag that
performs a transformation between device colors and PCS colors using
a particular rendering. For more information about 'clut' transformations,
see Section 6.5.7 of the International Color Consortium specification
ICC.1:2001-04 (Version 2) or Section 6.5.9 of ICC.1:2001-12 (Version
4), available at www.color.org.LUT TypeDescription
'AToB0'  (default)Device to PCS: perceptual rendering intent
'AToB1'Device to PCS: media-relative colorimetric rendering
intent
'AToB2'Device to PCS: saturation rendering intent
'AToB3'Device to PCS: ICC-absolute rendering intent
'BToA0'PCS to device: perceptual rendering intent
'BToA1'PCS to device: media-relative colorimetric rendering
intent
'BToA2'PCS to device: saturation rendering intent
'BToA3'PCS to device: ICC-absolute rendering intent
'Gamut'Determines which PCS colors are out of gamut for a given
device
'Preview0'PCS colors to the PCS colors available for soft proofing
using the perceptual rendering
'Preview1'PCS colors available for soft proofing using the media-relative
colorimetric rendering.
'Preview2'PCS colors to the PCS colors available for soft proofing
using the saturation rendering.
C = makecform('mattrc', MatTrc, 'Direction', direction) creates
the color transformation structure C based on a
Matrix/Tone Reproduction Curve (MatTRC) model,
containing an RGB-to-XYZ matrix
and RGB Tone Reproduction Curves. MatTRC is
typically the 'MatTRC' field of an ICC profile
structure returned by iccread, based on tags contained
in an ICC color profile. direction can be either 'forward' or 'inverse' and
specifies whether the MatTRC is to be applied in
the forward (RGB to XYZ)
or inverse (XYZ to RGB)
direction. For more information, see section 6.3.1.2 of the International
Color Consortium specification ICC.1:2001-04 or ICC.1:2001-12, available
at www.color.org.C = makecform('mattrc', profile, 'Direction', direction) creates
a color transform based on the MatTRC field of
the given ICC profile structure profile. direction is
either 'forward' or 'inverse' and
specifies whether the MatTRC is applied in the
forward (RGB to XYZ) or
inverse (XYZ to RGB) direction.C = makecform('mattrc', profile, 'Direction', direction,
'RenderingIntent', intent) is
similar, but adds the option of specifying the rendering intent. intent must
be either 'RelativeColorimetric' (the default)
or 'AbsoluteColorimetric'. When 'AbsoluteColorimetric' is
specified, the colorimetry is referenced to a perfect diffuser, rather
than to the Media White Point of the profile.C = makecform('graytrc', profile, 'Direction', direction) creates
the color transformation structure C that specifies
a monochrome transform based on a single-channel Tone Reproduction
Curve (GrayTRC) contained in an ICC color profile.  direction can
be either 'forward' or 'inverse' and
specifies whether the grayTRC transform is to be
applied in the forward (device to PCS) or inverse (PCS to device)
direction. ("Device" here refers to the grayscale signal communicating
with the monochrome device. "PCS" is the Profile Connection Space
of the ICC profile and can be either XYZ or L*a*b*,
depending on the 'ConnectionSpace' field in profile.Header.)C = makecform('graytrc', profile, 'Direction', direction,
'RenderingIntent', intent) is
similar but adds the option of specifying the rendering intent. intent must
be either 'RelativeColorimetric' (the default)
or 'AbsoluteColorimetric'. When 'AbsoluteColorimetric' is
specified, the colorimetry is referenced to a perfect diffuser, rather
than to the Media White Point of the profile.C = makecform('named', profile, space) creates
the color transformation structure C that specifies
the transformation from color names to color-space coordinates.  profile must
be a profile structure for a Named Color profile (with a NamedColor2 field).
 space is either 'PCS' or 'Device'.
 The 'PCS' option is always available and will
return L*a*b* or XYZ coordinates,
depending on the 'ConnectionSpace' field in profile.Header,
in 'double' format.  The 'Device' option,
when active, returns device coordinates, the dimension depending on
the 'ColorSpace' field in profile.Header,
also in 'double' format.

Syntax

C = makecform(type)C = makecform(type, 'WhitePoint',
WP)C = makecform(type, 'AdaptedWhitePoint',
WP)C = makecform('srgb2cmyk', 'RenderingIntent', intent)C = makecform('cmyk2srgb', 'RenderingIntent', intent)C = makecform('adapt', 'WhiteStart', WPS, 'WhiteEnd',
WPE, 'AdaptModel', modelname)C = makecform('icc', src_profile, dest_profile)C = makecform('icc', src_profile, dest_profile,
'SourceRenderingIntent', src_intent, 'DestRenderingIntent', dest_intent)C = makecform('clut', profile, LUTtype)C = makecform('mattrc', MatTrc, 'Direction', direction)C = makecform('mattrc', profile, 'Direction', direction)C = makecform('mattrc', profile, 'Direction', direction,
'RenderingIntent', intent)C = makecform('graytrc', profile, 'Direction', direction)C = makecform('graytrc', profile, 'Direction', direction,
'RenderingIntent', intent)C = makecform('named', profile, space)

Example

rgb = imread('peppers.png');
cform = makecform('srgb2lab');
lab = applycform(rgb,cform);

Output / Return Value

Limitations

Alternatives / See Also

Reference